Use bars showing percentage. This way you can compare the values to a scale on the side and to each other. You can't see a difference easily on a pie chart without annotation. With enough values, you likely can't tell 5% from 10%, and difference between a fragment on the left from a fragment on the right.
This is even worse in 3d pie chart which doesn't even preserve proportions in areas/angles, so splitting in 4 parts, bottom/top will be larger than left/right.
